The fifth and final round of polling will take place in some of Bihar's most backward pockets notorious for high percentage of poverty, illiteracy as well as migration.
The seven districts that will see voting are Kishanganj, Purnea, Araria and Katihar in Seemanchal region and Saharsa, Madhepura and Supaul in Kosi region.
Both the BJP-led four-party alliance led by Prime Minister Narendra Modi and the Grand Alliance of Chief Minister Nitish Kumar were locked in a bitter war of words before campaigning ended on Tuesday evening.
Muslims form 16.5 percent of Bihar's 105 million population. In the Seemanchal, however, they account for nearly 67 percent in Kishanganj, 37 percent in Purnea, 43 percent in Katihar and nearly 40 percent in Araria.
Yadavs live in large numbers in Madhepura and Saharsa in particular.
"Muslims and Yadavs will play a major role (on Thursday)," political activist Mahender Yadav said.
Hyderabad MP Asaduddin Owaisi's Majlis-e-Ittehadul Muslimeen (MIM) is contesting from six seats in Seemanchal region. This is the MIM's first entry in Bihar's electoral politics.
Controversial politician Pappu Yadav's Jan Adhikar Party is also in the fray in Kosi region. Both Owaisi and Pappu Yadav are wooing Muslim and Yadav voters.
Nationalist Congress Party leader Tariq Anwar is also confident of making a dent in his stronghold Katihar.
The fifth phase is crucial for Nitish Kumar and his allies RJD leader Lalu Prasad and the Congress as well as the Bharatiya Janata Party-led NDA in the keen battle to control the 243-seat Bihar assembly.
The BJP has been eyeing the Seemanchal assembly seats, banking on a possible division of Muslim votes.
In Kosi region, sensing the difficult challenge, BJP president Amit Shah had ordered party leaders to make Madhepura, Saharsa and Supaul their base during campaigning.
"Amit Shah has been working overtime for more than two weeks in the region," a BJP source said.
Prime Minister Narendra Modi addressed election meetings in each district and mounted a strong attack on Nitish Kumar, Lalu Prasad and Congress president Sonia Gandhi.
The BJP is banking heavily on Modi's appeal and is confident of the support of the upper castes - Brahmins, Bhumihar, Rajputs - and also hopes to gain the backing of other communities.
Allied with the BJP are the Lok Janshakti Party (LJP) of Ram Vilas Paswan and the Rashtriya Lok Samata Party (RLSP) of Upendra Kushwaha -- both union ministers -- and the Hindustani Awam Morcha of former chief minister Jitan Ram Manjhi.
In Seemanchal, the dominant mood among the Muslims appears to be anti-BJP.
Most Yadavs are likely to throw their weight behind Lalu Prasad and the Grand Alliance.
The BJP is hopeful of gaining an upper hand in Madhubani and Darbhanga districts.
About 1.55 crore voters will be eligible to decide the political fate of 827 candidates on Thursday.
In what critics said was an attempt to polarize voters on religious lines, BJP leaders raked up the issue of beef consumption and said that a BJP defeat in Bihar would set off celebrations in Pakistan.
Nitish Kumar and Lalu Prasad were equally aggressive in their campaign.
The millions of votes polled in the staggered elections that began on October 12 will be counted on November 8.